An engine is known that couples a mechanical pump, which circulates coolant, to the crankshaft through a clutch to operate the pump using rotational force of the crankshaft and disengages the clutch to stop operation of the pump. Clutches for switching the coupling state of the pump with respect to the crankshaft include a clutch having a drive-side rotational body coupled to the crankshaft and a driven-side rotational body, which is rotational relative to the drive-side rotational body. The clutch is maintained in the engaged state by pressing the rotational bodies against each other using magnetic force of magnets.
Such clutches include a clutch described in Patent Document 1. The clutch described in Patent Document 1 includes a coil. To disengage the clutch, energization control is performed on the coil to generate a magnetic field that cancels the aforementioned magnetic force.